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Deceitful_Frank
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It would appear that the exact composition of blu-tak is a trade secret as the manufacturers are tight-lipped as to what goes in to give the right
balance of stickiness and moldability.
It does have a density of 1.9g/cm^3 though and I am pretty certain the main filler is chalk.
Assuming that the binders and plastisizers have a density of about 0.9g/cm^3, this leads me to believe that the binder/plastisizer system makes up
around 50% by weight.... obviously alot less by volume due to the differences in densities of the ingredients... Hmmm, this may not be right as if
chalk is used it would be hardly worth adding it to add bulk as by volume it would only make up a small proportion!
Anyway it doesnt really matter what the binder/plastisizer is... it works and helps you to acheive a good solid loading density and increased bulk
strength of your HMTD!
Tomorrow I will be making ETN for the first time for some descent pressed caps and to plastisize this excellent nitric ester for use in my next shaped
charge.
For compositions I'm thinking either an 80:17:3 blend of ETN/NM/PIB. To plastisize the 80+% ETN with PIB, caster oil and motor oil or to try to
replace the inert filler in blu-tak with ETN.
The first blend would appear to be the most powerful due to the high percentage of active ingredients and as long as NM will dissolve PIB, there
should be no problems?
I can mix it all wet and then evaporate down to calculated weight for a dence plastique that really packs some punch! 
[Edited on 15-5-2006 by Deceitful_Frank]
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nitro-genes
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If you could obtain any self vulcanising tape, you are far better of isolating the Pib from this than from bluetac. I tried both, and the bluetac does
seem to have a slightly better binding ability, but is a mess to isolate in large quantaties. For the isolation from the self vulcanising tape, just
dissolve all of the tape at once in about 100 ml of gasonline, let it sit for a week, filtering out the tape is very easy, and precipitate the Pib
with 50 ml of acetone. Yield is about 18 grams of Pib, enough for >400 grams of plastique! Pib is precipitated very well by acetone, so I'm quite
sure that NM won't dissolve Pib very well also. 
Most simple solution is to use nitrocellulose from ping pong balls in combination with NM, this can form anything from a stiff gel to a viscous liquid
with more or less NC dissolved...
There is however another binder you can use. I've experimented a little with this one, in combination with DEP, but with much less results than with
Pib. You can find it in the typical clear school glue. It consist of nothing more than polyvinyl acetate with a solvent. PVA dissolves very well in
acetone and NM and can form high density PBX type explosives by pressing...
I've been thinking to use this also for the PETN/NG composition, since you reminded me that the 1,65 g/cc density figure from COPAE probably is the
density when pressed.
Under: "Penthrinits" in PATR there is also some information about the PETN/NG 4:1 composition, but this one gives a loading density of 1,49 g/cc, with
a maximum achievable density of 1,72 g/cc. I think these figures a more thrustworthy, since they are from the same reference, but the information in
PATR is more complete.
Detonation pressure thus is probably not as high as I had hoped. I wonder if intruducing a few percentages of polyvinyl acetate in PETN/NG will give
slightly higher densities. Another option is a melt cast of PETN/ETN, but even than, that air is just so hard to get out! Maybe I will give my
vacuumpump from the destilation setup another use soon!
[Edited on 15-5-2006 by nitro-genes]
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enhzflep
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Yeah, thanks again nitro. Turns out I had the wrong sort of wheels in the garage 
The blutak's been dissolved for ~1month, so had settled quite nicely. No real reason not
to finish that wheel off.
You mention NC and NM. Well have only got about 40 ping-pong balls left, Buuuut - what about double base powder? Have still got about 1.75kg of AS-30N kicking about. Bit more punch? (and cheaper to boot) $210 Aus for 2kg
10.5c/gram
Thank-you also quicksilver. I'd thought that method of mixing to be the better option, however was just a little impatient, and wanted plastique in
under 45mins. But will have a bash at the method you mentioned.
Man, I hate being a lazy, impatient bastard...
Find below the pictures of the concrete & a star-stake.... Sorry for the shit quality - they're captured frames from a low quality vid.
4gms and then 3gms
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nitro-genes
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Just finished my new SC. 
This time I used only prefabricated PVC parts from plumbing supplies. So, no sawing, sanding etc. was necessary to align the charge and liner
properly, which is bound to make a SC less precise...
The charge consists of, from left to right:
1: 60 deg. (no tulip shape this time), 0.5mm thick copper liner with rouded apex, total height of 21mm and diameter of 25mm.
2: PVC tube endcap, with the innerdiameter of the liner sanded out in the middle, acts as a fitting to hold the liner in place.
3: PVC screw endcap, as explosives container (38mm high, so 0.8 headheight) and as an endcap for the charge.
And assembled it looks like this:
Still some doubt about the filler, but probably just the PETN/NG. Volume of the container with the liner in place is 18 ml, so with a denisity of 1.5
g/cc for PETN/NG 4:1, It will need about 27 grams of HE, and thus only 5.5 grams of NG. This is still acceptable for me. The only thing I still worry
about is whether the NG will weaken the PVC to a great extent...Does anybody know this?
[Edited on 16-5-2006 by nitro-genes]
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quicksilver
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Tasking for granted that the NG is acid free I don't believe that you need have any concerns what-so-ever. The only issue with nitric esters and
plastic containers is a wierd one: IF diphenylamine is used as a stabilizer and there is still some acid in the material you will get a deep BLUE
stain. It has been one of the methods used time and again to identify a less than complete wash of nitric esters.
ETN is a wonderful thing. The more one delves into the mfg of ETN the more it seems a simple replacment for PETN. I highly recommend US1691954 as it's
some of the better work published. Merck v12 has it. And you could check out various threads too. The biggest issue is purity, crystal formation, and
nitration time. Once those issues are settled to your satisfaction, the material is truely awe inspiring in it's utility and stability.
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rot
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Nitro, Where is the standoff?
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Rosco Bodine
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Hmmm....I have never experimented with shaped charges
using liners , but just off the top of my head it looks wrong to me to me to have the conical cavity OD come
all the way out to the cylindrical OD of the columnar charge . The thin V shaped section just looks wrong
to me . If I were designing the thing , just going on intuition , the OD of the cone opening would be about
two thirds of the OD of the cylindrical columnar section ,
the end of the charge being a flat ring , rather than a
sharp edge like an open cored punch . I might even
make the flatted ring a bit wider so that the flat is
even a quarter the width of the column . The end section
of charge just seems to be too thin to be doing much of anything on that section of charge where the liner
comes all the way out to the OD of the column , it just
doesn't have sufficient cross section to be doing much
in the way of work of holding and forming a tight jet ,
but that is just my own visualization and thinking .....
I don't really know .....I just know that I would probably
build it the way I think it should work
It may even be that the columnar shape itself is not as
good as would be a gradually flaring column , something like
a trapezoidal keystone shape , to add some thickness even
further surrounding the conical liner . Anybody else
follow what I am saying here ?
Another thought I have had is a torus shaped charge
which has a trapezoidal cross section , but is a flared ring
having a conical shape , and detonated around the upper edge continuously by a synchronizer cylindrical charge which is apex initiated . This would
function as a lens to collimate
the initial jet and reenforce it .
[Edited on 16-5-2006 by Rosco Bodine]
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Deceitful_Frank
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They call it subcalibration and IIRC the cone should be around 70-80% the ID of the SC casing.
My last EGDN SC had a cone of 20mm width and an ID of the casing of 28 so 5/7 or 71%
This can be built into the design of the SC or the space in the casing around the base of the cone can be filled with an inert material to save
explosive.
For small devices however its often not worth the effort to save a gram of two of plastique... may as well just ignore the first few millimetres from
the base of the cone and use 70-80% of its diameter when calculating your standoff and headheight
Boat-tailing (beehiving) also helps to save explosive and increase efficiency. SC's could be designed in all manner of shapes but not everyone has
access to CAD software and a full metalshop... its often so much easier to stick with simple proven designs and just nitrate 30% more polyol!
[Edited on 16-5-2006 by Deceitful_Frank]
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Rosco Bodine
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I see , the " effective dimension " of the charge
is visualized as having that " dead end " thin
section being " sawed off " for purposes of calculating the standoff distance .
I just wonder if that thin
section could have unfavorable steering effect on the jet ,
because of the asymmetry of the detonation wave
cutoff where it goes below critical diameter in the thin
section . I guess it would depend on the explosive being
used , the degradation of the jet would be worse for
lower velocity and higher critical diameter explosives ,
and little concern for the faster and small critical diameter stuff .
[Edited on 16-5-2006 by Rosco Bodine]
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nitro-genes
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| Quote: | Originally posted by rot
Nitro, Where is the standoff? |
Lol, forgot to mention, I still have to saw off about 5 cm of 32mm pvc tubing that will be the standoff (2 times CD). This does not have to be very
precise though...
Subcalibration indeed ensures that the base of the cone also participates in jet formation. For PETN the critical diameter for high order detonation
is about 2mm, so for my charge about 20 mm of the 25 mm will be 100% effective maybe, but using subcalibration in combination with a composition
containing NG is just very difficult to realise. NG attacks almost every glue and plastic there is and the subcalibration has to be done by hand,
which makes a good alignment more difficult. Steel or other metal tubing instead of PVC is not an option, I really don't like shrapnel for that
matter...
As I noticed with the beehive charge, very small aberrations in the alignment will have a dramatic effect on jet formation, so although subcalibration
improves efficiency quite a bit, it also complicates things quite a bit.
I don't think subcalibration is that critical btw since Axt his .357 magnum bullets still did 2.5 cm of steel IIRC!
The most difficult things for a home made shaped charge are liner symmetry, the alignment of the liner in the explosives container and to a lesser
extend, the point of initiation in combination with the headheight. If one of these is slightly off, there will be no penetration at all, especially
with cone shaped liners. The rest, like heavy confinement, subcalibration, explosives composition etc. will only have an effect on the overal
efficiency or CD's of penetration...
[Edited on 16-5-2006 by nitro-genes]
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Chris The Great
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Remember that the jet travels much faster than the speed of the collapsing liner (6-10km/s vs ~2-3km/s). Most of the jet will be through the target
by the time the last edges of the cone finish collapsing, so even if they had a unfavourable effect, it wouldn't matter. It certainly wouldn't be
able to "catch up" to the rest of the jet and knock it off course or have other unfavourable effects.
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Deceitful_Frank
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You took the words right out of my mouth! ...or should I say fingertips! Yep, thats all I have to contribute this morning
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Boomer
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While speaking of fingertips...
Enhzflep I noticed you're a lucky bastard, since on that pic said body parts
are still present. NEVER mix HMTD with anything, it is chemically unstable
and much worse in this respect than its acetone sister. I personally
had it detonate into my face while plasticising, while it was already
a goo and the force used was less than what would have set off
dry powder. There are SEVERAL similar stories from other peaple,
IIRC two including auto-detonation sitting on a shelf.
Obviously you were lucky this time, or used a combination that is more inert,
but do you KNOW it would not have 'misbehaved' had you aplied
a little more force while mixing, or had used more/less/another solvent etc?
Try writing with your non-dominant hand, or even wipe your ass - it sucks believe me.
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nitro-genes
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Had the same thing, 7 grams of HMTD/NC plastique just went BOOOM! suddenly...I was sitting about 60 cm away from it, since I just stopped mashing it.
Small pieces of the cardbord and foil it was lying on went through my trousers in my knee (!) and I couldn't hear for two days. It's years ago now,
but still my right ear is not as good as my left. Still, I think I was just very
lukcy...
It is such a terrible experience really, the first few minutes I just walked around without knowing what had happened, then I saw the blood al over my
knee and the crater in the table... I stopped making HE's for more than a year after this, sometimes I wonder what is wrong with me to continue to do
this...
Boomer is right, PLEASE stop fucking around with that shit! If you continue using HMTD like this it is not the question IF an accident is going to
happen, only WHEN.
[Edited on 17-5-2006 by nitro-genes]
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HMTD
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Hello! I really like this thread. I saw the pictures with such amount of HMTD plastique with fingerprints on it. Now, Enhzflep, imagine: You just
mixed 7 gramms of plastique, you knead it with you WORK hand - this is more comfortable for you. You like it's consistency, it's so softy, you think
where to use such a good thing? Next moment it all disappears, you don't feel any pain, but the next second you see your hand, if it can be so
called now. The blood from broken arteries flows to the floor in the rythm of your heart. YOU HAVE NO FINGERPRINTS ANYMORE. You trying to stop
bleeding, you call to emergency, later you will spend a month in a hospital. Now you feel pain. Such a pain that you can't sleep. But it will be
later, when nothing you can change. But you still can. You think this is joke? The friend of mine partially lost his two fingers when only 0,3 g (
not 7!) of such a plastique detonated in his hands when he tried to form it. The rest amount spontaniously detonated after 5 days after accident. The
binder was clear Pib/polybutene liquid. Please, don't use HMTD in mixes and your devices!!! There are beautifull substances - high explosives, for
example, PETN. With such a binder they are more dense(I had 1.59 for 89/11) and powerful than anything with HMTD. As for me, now I use small amounts
of primary - just 0,02-0,05 g of PbN6 with powdery PETN. Good luck. Sorry for my English.
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rot
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I'dd say don't even use sensitive primary's like HMTD or acetone peroxide. they're just too dangeroes. I use Silver Acetylide, Wich is much safer
(didn't detonate when I crushed it between 2 metal plates).
I used to use Acetone Peroxide as primary but started using Silver acetylide after I once had it detonate when pressing it into a plastic tube. It was
0.5g, thank god I was holding the tube with pliers or I would have been a finger shorter.
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a_bab
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I once got a nasty explosion because of the Ag2C2; I'd say it's far more sensitive than the AP; maybe something like the mercury MF. Very static and
flame sensitive that is, if is well dried. It can bite.
I still have a small mark of embeded carbon/silver oxide under the skin as to remind me. The amount involved in the accident was maybe 1 gram, in a
plastic box no bigger than a film can but all the palm was heavily bruised and it really did hurt. Alot.
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quicksilver
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| Quote: | Originally posted by nitro-genes
Had the same thing, 7 grams of HMTD/NC plastique just went BOOOM! suddenly...I was sitting about 60 cm away from it, since I just stopped mashing it.
Small pieces of the cardbord and foil it was lying on went through my trousers in my knee (!) and I couldn't hear for two days. It's years ago now,
but still my right ear is not as good as my left. Still, I think I was just very
lukcy...
It is such a terrible experience really, the first few minutes I just walked around without knowing what had happened, then I saw the blood al over my
knee and the crater in the table... I stopped making HE's for more than a year after this, sometimes I wonder what is wrong with me to continue to do
this...
Boomer is right, PLEASE stop fucking around with that shit! If you continue using HMTD like this it is not the question IF an accident is going to
happen, only WHEN.
[Edited on 17-5-2006 by nitro-genes] |
The horrable but interesting thing is that the material detonated AFTER any physical contact or stimulus. THAT is exactly why I just can't see
experimenting with peroxcides. And 7 grams of HMTD/NC plastique is no small chunk of change! To propel cardboard into flesh is really something to
contemplate.... I suppose that the issue is that from an experimentor's perspective it's availability and lack of expense is attractive. but there are
so damn many alternatives. Especially if one buys several pounds of Erythritol or Mannitol. The thing is that those sweeteners are available to anyone
for pennys (send me mail & I'll be happy to give URLs).
It just goes to show how vastly unpredictable HMTD / AP are and how uniquely addictive this damn hobby is as well.
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rot
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Let's go back on topic.
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enhzflep
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Shit, God dammit. So those pics I've seen of a hand missing fingers were from you Boomer, the very one and the same? Along with the little boy that
chewed on a detonator, the BP fountain imbedded in knee and the CO2 bulb that passed through somebody's leg. OUCH. Never mind the guy that was cubed
by a pipe bomb.
It is therefore the case that I must say thank-you to Boomer. For I never tried plasticizing the shit until after I read your post at RS.org. Read
about (kewlish) efforts to 'plasticize' AP with double base powder (10%Ng, 90%NC). Hey I even gave it a bash once, but that stuff is not very friendly
- the AP recrystalizes into HUGE crystals. So, reading your post along with the AP experiment and seeing that picture of your hand caused me to
never, ever want to try mixing it with NC and or NG.
So, anybody got an idea of what I should do with the 15gm chunk of the stuff I've had sitting outiside for the last 5 days? Guess I should leave it
away from the 50gms sitting in the pyrex jug...
But seriously - I guess you could put it down to having somewhat of a cavalier attitude towards the stuff, not (just) simple ignorance. I first spent
about 10 hours looking across the net for accidents involving the stuff. The thing that was overwhelmingly in common with these accidents was (A)
mixing with NC, (B) mixing with DB powders or (C)pressing into containers made of incompatible metals(in which case, any moisture would increase rate
of decomposition). To be perfectly frank, the remainder I put down to "operator error" as it were, judged on account of the apparent poor grammar,
scientific technique and lack of understanding of the seriousness of the compound exhibited by those unfortunate many.
Over the course of several dozen batches I have altered the method used to wash and neutralize it. It is in my experience, much, much harder to free
the substance of all traces of potassium carbonate or sodium bicarbonate than it is to free the substance from citric/hydrochloric acid. Therefore I
don't neutralize it, but merely wash it. I borrow a ph meter with 3 sig figures, and use a biometric sensor too (my tongue)
Anyway- after 4months of sitting, a mixture that has been neutralized detonates with a distinctly different smell and much reduced flame. Not to
mention the fact that said powder retains clumps as a result of moisture retention. Almost smells like a coke fire furnace.
After the same period a batch that has been washed and washed and washed again (some 10 - 15 times) reacts _precisely_ the same as it did on the first
day it was dried. Not only is there no funny smell or flame reduction, but the powder is as free flowing and fine as powdered glass - an indication of
the lack of water absorption/retention.
The binder from blu-tak was chosen for several reasons.
1) It's non-toxic and safe for children to play with/eat (so long as they don't choke on the stuff) This is an indicator that it is an inert
substance. Along with the claim of the inertness of its binder in Bostik's MSDSs. One may leave a blob of the suff sitting in the open air for months
and months and months at a time without any observable change on the surface - it never hardens or dries out i.e no observable volatility or
oxidisation taking place. Although UV light's not its best friend.
2)Its readilly available and comes from a well respected company with too much of a reputation to protect to produce batches with significant varience
in physical/chemical properties. Though I'd obviously be in no position to sue for a change in composition
In addition to these facts, I started out mixing some 0.2 - 0.3gms of hmtd with the blu-tak binder. This first sample was divided into two. One sample
went into the oven at 60deg C where it sat without incident for 4 days, while the other half went into the freezer. At the end of the four days, each
sample was again divided into two, meaning that I now had 4 balls. One ball from each storage method was tested with hammer and anvil, the other 2
balls were tested with flame.
Results: Hammer testing was significantly harder to initiate than straight powder - with no discenrable difference between two two storage methods. -
Also noted was the fact that incomplete detonation was observed, a small blob remained on anvil after testing. Scraped up, this was still
dentonatable.
Flame testing was similarly uneventfull,although very nearly as sensitive to flame/spark as straight powder - it must be noted that the burning did in
fact proceed somewhat slower than a similar quantity of straight powder would.
NOW,
All that said. Thank-you, one and all for your concern. This is pehaps the appropriate time to get a new flavour of the month. (while i can still type
& shit with gay abandon) Programming the new version of HECalc is hard enough
with two hands
I guess ETN should be next. Besides, as video from Axt and Nitro-genes have clearly shown this material has great utility for the construction of
shaped charges.
Has anybody thought along the same lines as myself, in that a flexible linear SC could be quite effortlessly constructed using copper
powder and latex-rubber? (or other similarly flexible, curable product- possible silicone sealant...)
*Imagine if you will, firstly filling the bottom ~ 1/2 of U-channel with latex rubber. Then laying a piece of 90deg angle into this
*Following this, a thin layer of (safe) plastique would be inserted, before having a cavity formed in it with a square rod.
*Next would come the pouring in of a latex/copper mixture, to act as the liner. This too would have a cavity former inserted
*Finally, latex could be poured ontop and allowed to cure.
-I imagine this to be somewhat similar to the method utilized by commercial manufactures of said product. Albeit with certain efficiency (and possible
continuous, i.e extrusion) techniques.
I have attached a diagram that should better describe what I mean below.
[/cavalier attitude]
Look forward to the new version of HECalc coming in the next week or so. Includes library of explosives, better numerical methods, Calculation of OB
and VDet for multiple compounds, output saving and comprehensive help.
enhzflep.
EDIT:
And yeah. I do realise I've misspelled mold as mould in the very first line. Oh well, too lazy to edit image and re-post....
[Edited on 18-5-2006 by enhzflep]
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nitro-genes
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Last night I tested the 25mm shaped charge with PETN/NG. This stuff is dense! I measured the volume of the container to be about 18 ml, and because
PATR mentioned PETN/NG 4:1 to have a loading desity of 1.49 g/cc I thought I'll make 28 grams total to be sure to have enough. Turned out I was still
about 1-2 grams short...
What can I say, the report was an incredibly thight thumb really, in that sense noticably different from the PETN/Pib composition. The movieclip is
nothing special, since the mixture is pretty oxygen balanced. But the reverb coming from the nearby water was great.
Fairly good results this time, I used the length of the small block of steel this time, which is 7.5 cm long and 2.5 cm thick! The jet came very close
to penetrating the whole block, as well as almost completely splitting it. 
I measured the depth of penetration with a long thin needle and came to a decent 6.8 cm. Still, not even close to the 4 CD+ specs such a charge should
do.
Again there was the same copper coloured dimple (grey circle in the first picture) next to the enrtyhole, just like with the last one. Very strange,
since the first shaped charge did not show this. There was no carrot in the penetration hole, so that may have been the cause of the dimple. Precision
really is key for a good shaped charge I think...Then again, how can there be a reasonably good jet formation with the carrot beeing more than a
centimeter off center?!
I've systematically demolished all of my steel blocks now, so I'll have to find some replacements. The next charge will be done underground, so with good sand tamping. and some subcalibration. I expect a much tighter
and deeper penetration for this setup, maybe 4 CD will be within reach!
[Edited on 18-5-2006 by nitro-genes]
Attachment: 25mm PETN+NG SC small compressed.avi (919kB)
This file has been downloaded 1606 times
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enhzflep
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Now, that is a pretty picture.
From previous experiments with last month's flavour of the month, I was able to determine that when I used a plastic body rather than a metal one, I
only got about 1/2 as much penetration. Certainly, i think the effect may well be less with a faster compound, but applying the same formula to the
penetration shown above would give you about 13.6 cm - some 5.5 CDs. I forget the name and location of the file, but I believe Axt has posted a file
detailing a study into the effects of changing the strength of confinement.
(It was a jpg from memory)
I really wouldn't have been doing more than pissing into the wind about the dimple, UNTIL i read some posts in the last 2 or so pages of this forum,
Re: critical diameters of explosives. My $5 says that once you get subcallibration with at least the critical diameter of your explosive around the
base of the cone, that you will no longer have the carrot being blown off center.
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nitro-genes
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| Quote: | Originally posted by enhzflep
I really wouldn't have been doing more than pissing into the wind about the dimple, UNTIL i read some posts in the last 2 or so pages of this forum,
Re: critical diameters of explosives. My $5 says that once you get subcallibration with at least the critical diameter of your explosive around the
base of the cone, that you will no longer have the carrot being blown off center. |
It can't be the whole story, since the beehive charge with the 25 mm liner had the largest subcalibration of the three charges (2.5mm), and had the
dimple/stain next to the entry hole also!
I think I might have been not precise enought with the drilling of the detonator hole in the endcap. But this could be half a millimeter at the most.
Another thing could be fluctuating densities or even small airgaps in the explosive at the base of the cone. I agree that the collapse of the base of
the cone is most likely the problem, but again, the beehive charge did also have this problem... It can't be the liner though since the penetration of
the first charge was perfectly symmetrical with a smooth appearance...
Confinement is something I still want to try, although sandtamping probaly is not as effective as a steel wall...
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quicksilver
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Could it be that the strength of the whole need be equal? That is that if there exists a greater strength to the cone than the body or visa versa that
differing results occur? The example of a small cone made from a bullet casing comes to mind. Here the cone is weaker than the body. However, the
elastisity of the whole is mostly equal. PVC, etc may be quite strong in terms of containment due to it's flexability. Could that very factor be an
influence?
Most commercial SC have less varience in wall and cone flexability it appears....just a thought.
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Joeychemist
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Registered: 16-9-2004
Location: Canada
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I'm looking for literature pertaining to kinetic energy of jet impact vs. work of plastic deformation of various target materials.
Any refs would be appreciated
[Edited on 24-5-2006 by Joeychemist]
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